﻿using System;
using System.Collections;

namespace OnlineBookstore
{
    public abstract class cl_0423_MySubject
    {
        protected ArrayList observers = new ArrayList();

        public cl_0423_MyObserver cl_0423_MyObserver
        {
            get => default;
            set
            {
            }
        }

        public void attach(cl_0423_MyObserver observer)
        {
            observers.Add(observer);
        }

        public void detach(cl_0423_MyObserver observer)
        {
            observers.Remove(observer);
        }
        public abstract void active();
        
    }
}